Helical structures and water vapor sorption properties of carrageenan membranes derived from red algae

Abstract

Packaging manufactured from petroleum is stable, and its waste threatens marine life. This study proposes the use of harmless edible materials manufactured from marine plants. Carrageenan is among the natural polysaccharides derived from red algae. Water vapor sorption was studied for membrane specimens of κ-carrageenan, ι-carrageenan, and λ-carrageenan at 25 °C. κ-Carrageenan and ι-carrageenan showed double-helical structure, whereas λ-carrageenan exhibited a single-helical structure. In the solubility test of liquid water, κ-carrageenan and ι-carrageenan were swollen, and λ-carrageenan dissolved in water at 23 °C. However, these higher-order structures were maintained after the exposure of water vapor to a relative pressure of 0.9. The water vapor sorption properties in carrageenan membranes were related to the relative pressure and categorized into three relative pressure ranges, namely, from 0.0 to 0.3, from 0.3 to 0.6, and from 0.6 to 0.9. The amounts of water molecules sorbed in the membrane were correlated with the number of polar groups in each carrageenan from 0.0 to 0.3. From 0.3, the cluster of water molecules started to appear with the maintenance of the helical structures. This novel finding can potentially lead to the design of environmentally friendly packaging by using carrageenan.

Keywords

• Helical structure
• Polysaccharides
• Red algae
• Carrageenan
• Water vapor sorption
• Barrier membranes